1. Field of the Invention
The present invention relates to dot-matrix printing mechanisms for printing characters using a character generator in which the printable characters are stored in binary form in rows and columns of character elements and having a control unit for controlling the advance of a print head post-connected to the character generator.
2. Description of the Prior Art
Characters may be printed by dot-matrix (mosaic) printing devices either with a fixed spacing between adjacent characters or with a proportional spacing between adjacent characters which is adjusted according to the width of the character to be printed. Material printed utilizing fixed spacing between the characters has a substantially poorer overall general impression of the print image than does material printed with proportional spacing. A character generator is known from U.S. Pat. No. 4,071,130, corresponding to German OS No. 26 03 347 for use with dot-matrix printing devices which have fixed character spacing. The characters are stored in matrix-like storage areas of equal size. When a character is called, these storage areas are scanned column by column, each column in a storage area being assigned a single advance increment for the print head of the device. Because each character does not occupy the entire storage area, varying amounts of blank columns will be present on either side of a character centered in the storage area, so that when the entire storage area is utilized for printing adjacent characters, the spacing between the printed characters will not be uniform.
For generating proportional character spacing in the context of dot-matrix printing devices in which the print head advances by an amount corresponding to the width of the character, a special character generator is commonly used in which a combination is assigned to each individual character and contains information regarding the character width. In order to enable the printing mechanism to advance the varying lengths of travel which are necessary in this system, the character generator must be sampled by an involved process in order to obtain this information, with the information subsequently being supplied to control electronics. Such a character generator for proportional spacing is thus considerably more complex in construction and circuit outlay than a character generator for generating characters with fixed spacing.